Not Applicable
Not Applicable
1. Field of the Invention
The present invention relates generally to air inlet or throttle valves, and particularly to throttle valves of the butterfly type utilized for controlling air inlet flow to an internal combustion engine.
2. Description of the Related Art
In recent times, with the advent of onboard microprocessor controllers for vehicle engines, it has been desired to provide electrically operated control of the vehicle engine throttle in order to more fully utilize the sophistication of the programs contained within the microprocessor for engine fuel delivery and ignition timing control in order to minimize fuel consumption and reduce exhaust emissions. It has also been desired to integrate the throttle control with the onboard engine microcomputer as an adjunct or override for vehicle operator throttle pedal movement. It has further been desired to provide an electrically operated throttle in order to implement the cruise control function and traction control function with the algorithms programmed into the engine control computer.
Heretofore, it has been proposed to provide an electric motor mounted on the vehicle throttle body to provide throttle valve rotation in response to an electric control signal provided by the vehicle engine computer. However, it has proven difficult to mount an electric motor on a vehicle throttle body and provide proper calibration of the motor for precise positioning and rotation of the throttle after mounting of the motor on the throttle body.
Heretofore, it has been proposed to provide stepper motors and relatively high rotations per minute (rpm) low torque servomotors connected through a speed reducing gear train to provide electrical actuation of the vehicle throttle. However, stepper motors can be prohibitively costly for high volume automotive applications; and, servomotors driving the throttle through a gear train can be difficult to calibrate and can lag in providing the necessary response time required for vehicle throttle operation. It has also been proposed to use a torque motor for direct throttle rotation. However, torque motors can be prohibitively heavy and bulky in order to provide adequate torque for desired throttle response. Torque motors can also be difficult to assemble on the throttle body and calibrate for proper throttle positioning. Furthermore, torque motors can require installation and precise calibration (i.e., rotary orientation) of the motor stator and rotor poles with respect to the throttle plate before assembly of the throttle body to the engine intake manifold. However, when it is desired to fabricate the throttle body and engine intake manifold as a single one-piece member, all motor actuators can be quite difficult to assemble and calibrate on such an arrangement.
U.S. patent application Ser. No. 09/098,974 titled Electrically Operated Throttle Valve Assembly, assigned to the Assignee of the present invention and hereby incorporated by reference, describes a throttle valve assembly design where the rotor is supported by the throttle valve shaft. In this design, the shaft 18 extends outward beyond its support bearing by the length of the motor as best seen in FIG. 1.
There still exists a need for an improved design that can reduce the bending moment produced by shaft 18 and mount stator 34 without fasteners positioned in the magnetically critical pole outer diameter (O.D.) area therein.
Still, it is desirable to provide a relatively low cost, lightweight, motorized throttle for a motor vehicle engine which is simple to fabricate, fast in response, lightweight, and requires little or no calibration upon installation.
Accordingly, one object of the present invention is directed to reducing the bending moment of the throttle shaft, i.e., reducing displacements during vibrations.
Another object of the present invention is to shorten the throttle shaft to increase the stiffness of the rotor assembly. This allows for a slightly smaller magnetic air gap and results in improved magnetic efficiency. Shortening the shaft reduces the inertia due to the shaft which results in improved response time.
A further object of the present invention is to reduce or even eliminate attachment bolts from the magnetically critical pole area of the stator assembly.
Still a further object of the present invention is to provide a torque motor assembly design that allows for more winding area in the laminates for a given motor size by providing an increase in the slot area available for winding magnet wire around each pole of the stator. This can result in a smaller motor for the same torque.
Still a further object of the present invention is to provide a torque motor assembly design that allows for more magnetic flux for a given motor size.
The present invention provides an improved torque motor assembly design constructed preferably integrally with a throttle body and valve with the motor having a rotor attached to an extending portion of the throttle shaft. Preferably a portion of the throttle shaft extends exteriorly of the throttle body with the motor rotor configured as a hollow cylinder and mounted on the shaft and nested concentrically over the stator. The preferred embodiment of the present invention eliminates the mounting bolt(s) for the attachment of metal laminations to the stator assembly, and replaces that design with a welded, wound, and overmolded stack of laminations. The present invention provides a design with an increase in the slot area available for winding magnet or electrically conductive wire around each pole of the stator. In an alternate embodiment of the present invention, a second shaft is provided substantially centrally through the stator in a less magnetically critical area, i.e., the inner diameter (ID). The second shaft is preferably a through-bolt smaller in diameter than the throttle shaft. The second shaft is rigidly attached to a housing that concentrically surrounds the stator and rotor.
The various features of novelty which characterize the present invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of this invention is illustrated.